$ { {2} \times \left[\begin{array}{rr}{3} & {0} \\ {0} & {0} \\ {-1} & {3}\end{array}\right] = {?} } $
To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rr}{2}\times{3} & {2}\times{0} \\ {2}\times{0} & {2}\times{0} \\ {2}\times{-1} & {2}\times{3}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{6} & {0} \\ {0} & {0} \\ {-2} & {6}\end{array}\right]}$